Apparatus for helixing and sorting filmed resistors



May 20, 1969 v MANDONAS ET AL 3,444,782

APPARATUS FOR HELIXING AND SORTING FILMED RESISTORS Filed May 20, 1966 Sheet of 5 INVENTORs 11mm;

y 0, 1969 N. J. MANDONAS ET AL 3,444,782

APPARATUS FOR HELIXING AND SORTING FILMED RESISTORS Sheet g of5 Filed May 20, 1966 May 20, 1969 N. J. MANDONAS ET AL APPARATUS FOR HELIXING AND SORTING FILMED RESISTORS Filed May 20, 1966 Sheet A ofa/ I l l l 4 e4 kid/e5 547152 1206 May 20, 1969 N. J. MANDONAS ET AL 3,444,782

- APPARATUS FOR HELIXING AND SORTING FILMED RESISTORS Sheet Filed May 20, 1966 United States Patent 3,444,782 APPARATUS FOR HELIXING AND SORTING FILMED RESISTORS Nicholas J. Mandonas, Medford, and Norman F. Smith,

Methuen, Mass., assignors to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed May 20, 1966, Ser. No. 551,771 Int. Cl. B23c 3/28 U.S. Cl. 90--11.64 11 Claims ABSTRACT OF THE DISCLOSURE Apparatus uses a pivotally mounted rotary saw to make helical cuts in films on ceramic cores. The saw pivots downwardly into an intermediate position, close to a core, then drops onto the core without rebounding, therefrom as portions of two cams are removed successively from support of the saw. A magnet holds the saw at a desired depth of cut. The saw is mounted for adjustment to follow a desired angle of helix. Preliminary and continuous resistance tests govern the cutting of each helix to bring the film resistance to a desired value.

This invention relates to apparatus for helixing and sorting filmed resistors, and more particularly to a carbon deposited resistor helixing machine having facilities for sorting resistors in accordance with initial and final parameters together with a machine interrupting device operated upon ascertaining a predetermined percentage of resistors failing to satisfy the initial and final parameters.

In helixing resistors to value by cutting a groove in a carbon film deposited on a ceramic core of each resistor, it has been found that a resistor is unacceptable when the required resistance value is reached before the helix ing has progressed over a sufficient percentage of the length of the resistor blank. Resistors helixed to less than a minimum length are likely to have films deposited thereon which are too thin and may develop hot spots in the area of the helixing, causing damage due to overheating. A value of 75 percent of the resistor length has been found in practice to be a useful minimum length for helixing. It is desirable, therefore, to provide for rejection of resistor blanks which have the correct resistance value, but which have attained that value by helixing over too short a length. It is also desirable to provide quality control by shutting off the apparatus when the rate of rejection becomes too high.

Additionally, if the initial resistance of the resistor blank is much too high, typically when an uncoated ceramic core is used through error, it is desirable that the cutting apparatus never be actuated. Thus, it is advantageous to preliminarily measure the initial resistance of the resistor film and to provide for helixing only when the initial resistance is below a predetermined value. A rejection mechanism for segregating out unhelixed resistors and a shut oif feature for high rejection rates are also desirable to cover the situation in which cutting does not occur.

It is an object of this invention to provide a new and improved apparatus for helixing and sorting filmed resistors.

Another object of this invention is to provide an apparatus for adjusting the resistance of a resistor blank to a desired value by cutting a groove therein having at least a minimum length and for segregating out resistors of the desired resistance value having grooves of less than the minimum length.

It is also an object of this invention to provide an apparatus for adjusting the resistance of a resistor blank to a desired value, which apparatus will preliminarily measure the initial resistance of the resistor blank and will cut to the desired value only those blanks having initial resistances below a predetermined resistance, while rejecting and segregating out the other, uncut blanks.

Concomitant with the other objects, it is a further object to provide for the shutting oif of such apparatus when the rate of rejection exceeds a predetermined level because too high an initial resistance is measured.

With these and other objects in view, the invention contemplates apparatus wherein a rotating saw is mounted adjacent a resistor blank support for motion into contact with a blank and motion transversely along the blank, wherein mechanisms are provided to bring the saw into cutting contact with the carbon film on the resistor core and to cause the saw to travel along the blank and then to return to its initial position when the resistance of the carbon film has reached a desired value, and wherein a mechanism is provided for allowing resistors which are cut to at least a desired minimum length to enter a receptacle while segregating out other, rejected resistor blanks. More particularly, a segregating gate is used to deliver resistors to either of two receptacles, depending upon the length of cut, while a counting mechanism compares the number of rejects counted with time measured by a timer and controls a shut off mechanism which will shut on the apparatus to prevent continued operation at high rejection rates. An initial resistance reading is made by a test set and this reading determines whether cutting will occur while provision is made for segregating out uncut resistor blanks by using the segregating gate, as well as the control afforded by counting mechanism, the timer and the shut off mechanism.

Other objects and advantages of the invention will be apparent from the following detailed description when considered in conjunction with the accompanying drawing, wherein: 1

FIG. 1 is a side view of a finished resistor having desired resistance value and having a length of cut greater than a desired minimum length;

FIG. 2 is an end view of apparatus for adjusting the resistance of filmed resistors;

FIG. 3 is a top view of the apparatus illustrated in FIG. 2 showing spindles for holding the resistor leads during cutting;

FIG. 4 is a side view of apparatus illustrated in FIGS. 2 and 3, showing a resistor being cut to the desired value;

FIG. 5 forms the top portion and FIG. 6 forms the bottom portion of a simplified schematic diagram of the control circuit of the invention; and

FIG. 7 is a schematic diagram illustrating the operating cycle of the rotary switches RS1 through RS-6 of the control circuit.

Referring now to FIG. 1 of the drawing, there is shown a resistor 11 of generally cylindrical shape having leads 12 extending from caps 13 at either end. The resistor has a ceramic core 14 on which there has been deposited a carbon resistance film. The initial resistance of the film, prior to helixing, is less than a desired resistance value for the resistor 11. In order to raise the resistance to its desired value, a helical groove 16 is cut into the carbon film, starting near a cap 13 and running along the resistor until the desired resistance is obtained. The resistance increases With helixing due to a lengthening of the resistance path and a decrease in the cross section area of the carbon film through which a current can pass. The length of helix is designated as L in FIG. 1, while the overall length of the resistance film is identified as L It is desirable that the resistor reach its final resistance value in not less than a desired minimum length of helixing, shown in FIG. 1 as L L is taken to be percent of L as a useful value in practice. As L is clearly greater 3 in length than L in FIG. 1, resistor 11 may be regarded as an acceptable finished resistor. Were L to have been less than L when the desired resistance value was reached, the resistor would have been rejected. Also, the resistor would have been rejected if it had failed to reach the desired resistance value when L became equal to L Turning now to FIGS. 24, a conventional indexing wheel 17, shown schematically in FIG. 4, which is intermittently driven by a wheel indexing stop motor (not shown), has spaced about its periphery a plurality of recesses 18 for holding resistors 11. Two spindles 19 are positioned one at each side of wheel 17 and adjacent to the periphery of the wheel. The spindles are adapted to close about a resistor 11 in cutting position so that each of the leads 12 is carried by one of the spindles in an opening 21 therein and is maintained in electrically conductive contact therewith while holding the resistor electrically isolated from the cutting mechanism which is at ground potential. Spindles 19 are opened and closed by solenoid valve controlled air reciprocating rotary cylinders (not shown). The spindles are also rotated about their central axes by a spindle drive motor (not shown) in order that a helical cut may be made in the surface of a resistor 11.

A rotary saw 22 is positioned adjacent the space between spindles 19 and is mounted at one end of a pendulum arm 23 for rotation about center 25. The pendulum arm is suspended from a supporting pivot 24 near its upper end 26. Any suitable drive train, such as belts 27 and 28, pulleys 29, 30 and 31 and reduction gear mechanism 32, may be used to transmit rotary cutting power to saw 22 from a suitable motor (not shown). An arm 33 extends outwardly from pendulum arm 23, preferably perpendicularly to the pendulum arm in a direction away from index wheel 17. Preferably, arm 33 is located so that an extension of its center line would intersect the center line of pivot 24. Arm 33 is positioned to pivot pendulum arm 23 about pivot 24 to cause saw 22 to be removed from the carbon resistance film on resistor 11 when arm 33 is lifted by a cam 34 operated by a saw up rotary solenoid 36. Weights may be added to, or removed from, arm 33 to suitably balance the pendulum arm assembly.

Adjacent the upper end 26 of pendulum arm 23, a second cam 37 is mounted, as seen in FIGS. 2 and 3. The operation of cam 37 is controlled by a second rotary solenoid 38. Cam 37 is positioned to act upon an arm 39 extending outwardly at upper end 26 of the pendulum arm to pivot the pendulum arm about pivot 24 so that saw 22 is located otf the resistance film on a resistor 11, but spaced therefrom by a relatively small distance. A spacing of 0.032 inch has been found useful in practice in apparatus having a pendulum arm 23 which extends for four inches between the supporting pivot 24 and the center 25 of saw 22. This spacing permits cam 37 to act as a temporary stop, when cam 34 is not being actuated by its rotary solenoid 36 to keep saw 22 pivoted away from a resistor 11. Thus, saw 22 may be held by cam 37 in this stopped position, close to the resistor 11, and then released by actuating rotary solenoid 38 to retract this temporary stop by withdrawing the lift portion of cam 37 from arm 39. Saw 22 may, thus, drop lightly onto the surface film of resistor 11 with a minimized tendency to rebound therefrom.

Also mounted adjacent the upper end 26 of the pendulum arm are an electromagent 41 and a projecting stop 42. An adjusting mechanism (not shown) for adjustably positioning the projecting stop is preferably provided. Electromagnet 41 and stop 42 are so positioned that the electromagnetic force will act upon upper end 26 of pendulum arm 23 to hold saw 22 against the resistor when cams 34 and 37 are in position to permit the saw to contact the surface of resistor 11. Saw 22 is allowed to move in and out so that the saw will follow the contour of the resistor, which may have an irregularity on its surface or an elliptical core, or may be eccentric between caps 13.

The depth of cut is controlled by controlling the electromagnetic force on the pendulum arm. The stop 42 may be adjusted so as to not allow the saw 22 to cut a backup roller (not shown) when there is no resistor in place.

The pivot 24 for supporting the pendulum arm is mounted between two mounting arms 43, which also carry cams 34 and 37, solenoids 36 and 38, magnet 41 and stop 42. Mounting arms 43 are themselves carried on a mounting block 44. As seen in FIGS. 2 and 3, mounting block 44 is composed of a longer central member 46 and a pair of shorter side members 47, preferably integrally formed as a single block. A mounting block pivot pin 43 passes through longer central member 46 at a point below the lower ends of shorter side member 47. The mounting block pivot pin is carried by a pair of upward projecting portions 49 extending from a saw mounting assembly supporting member 51. The bottom surfaces of mounting block side members 47 end in a pair of pivot points 52 which are adapted to pivot on the top surfaces 53 of the supporting member upward projecting portions 49 as mounting block 44 pivots on mounting block pivot pin 48. This mounting arrangement permits the tilting of mounting arms 43 and the entire assembly carried by these arms about the axis of pin 48 to tilt pendulum arm 23 and saw 22 to parallel the desired angle of helix on resistor 11. This assembly is maintained in the selected tilted position by tightening locking screws 54 in projecting portions 49 against mounting block central member 46.

Saw mounting assembly supporting member 51 is mounted for reciprocation parallel to resistor 11 on a pair of horizontal members 56. A suitable saw carriage reciprocating motor (not shown) rotates a traverse cam 57 having a groove 58 therein for causing traverse reciprocation of the saw mounting assembly necessary for helixing. A follower 59 rides in groove 58. The follower is interconnected with saw mounting assembly supporting member 51 through any suitable reciprocating linkage, such as links 60 and 61, adjustably connected together at 62.

Positioned beneath spindles 19 are a pair of receptacles 63 and 64 (FIG. 4). Rejected resistor receptacle 63 accepts those resistors which are considered bad, because their initial resistances are too high, because they have reached the desired resistance value before being helixed across 75 percent of their lengths, or because they have not reached the desired resistance value when helixed the entire length. Good resistor receptacle 64 accepts finished resistors having the desired resistance value and helixed across at least 75 percent of their lengths. A segregating gate 66, suitably pivoted at 67, is normally held by a rotary solenoid 68 in the bad resistor position shown as the clockwise position in FIG. 4, closing off good resistor receptacle 64 to bad resistors and permitting these resistors to enter bad resistor receptacle 63. A biasing mechanism, such as one or more springs (not shown), is positioned to drop segregating gate 66 in a counterclockwise direction to a good resistor position, when rotary solenoid 68 is not energized. In this position, bad resistor receptacle 63 is blocked and good resistor receptacle 64 is open to accept good resistors.

In describing the operation of the apparatus, reference is now made also to FIGS. 5-7. FIG. 7 is a chart which depicts the cycle of operation of six cam actuated switches, shown in the circuit of FIGS. 5 and 6 and designated .as RSl through RS6. The degree markings represent the attitude of the six associated cams, designated C-1 through C-6, respectively, in FIGS. 5 and 6, which are mounted on a common shaft and driven by conventional means, such as the saw carriage motor designated by numeral 76 in FIG. 5, which operates traverse cam 57. At the cam position labeled 0, for example, switch RSl is shown to be in its up position, switches RS-2 and RS3 to be in their down positions, RS4 and RSS to be closed, and RS-6 to be open.

In the operation of the apparatus, a main switch 71 and then an on switch 72 are first closed. Single phase alternating current is thus introduced to a transformer 73 and current passes through closed switch 72 to energize a main relay 74. Relay 74 closes contacts at 74-1, 74-2, 74-3, 74-4, and 74-5. The closing of the first three of these contacts provides power to the carriage drive motor 76, for rotating cam 57 to reciprocate the saw carriage, and to a spindle drive motor 77, for rotating the spindles. The closing of the contacts at 74-4 permits current to continue to fiow to main relay 74 after the release of on switch 72, while the closing of contacts 74-5 provides power across a bus 78 and a bus 79.

A start cycle switch 81 is next actuated to provide current to a cycle control relay 82, causing the closing of contacts at 82-1 and 82-2. The closing of contacts 82-1 permits current to continue to flow to relay 82 after switch 81 is released. The closing of contacts 82-2 provides power across a bus 83 and bus 79.

When power is supplied across bus 83 and bus 79, a saw motor 87 for supplying power to rotary saw 22 is energized. Electromagnet 41 for maintaining the saw cutting depth substantially constant is also energized. An autotransformer A allows easy control of magnetic flux in the electromagnet 41 to regulate the depth of the saw cut.

The cams C-1 through C-6 are now in the vicinity of the zero degree position of FIG. 7, i.e. they are positioned between 315 and Thus, open spindles switch RS-3 is presently in its down position. Current, therefore, flows to a latch relay 91. Relay 91 closes contacts at 91-1, 91-2 and 91-3. Contacts 91-1 are in a line to the unlatch mechanism of latch relay 91, while contacts 91-2 are in a line for energizing wheel index motor 92 and contacts 91-3 are in a line for supplying current to an open spindles solenoid valve 93.

A spindles open limit switch LS-l of conventional type is positioned in the apparatus to be closed when spindles 19 are open. Since the spindles are now open, switch LS-l is closed and current flows to a spindles open relay 94 which opens a pair of contacts -94-1, while closing contacts 94-2. The opening of contacts 94-1 creates an open circuit in the line to open spindles solenoid valve 93. Meanwhile, the closing of contacts 94-2 energizes wheel index motor 92 since contacts 91-2 have been closed and a pair of normally closed contacts 96-1 are presently closed. Wheel 17, thus, begins to index a resistor 11 toward its proper position adjacent spindles 19.

The start of the indexing movement causes an appropriately positioned conventional limit switch LS-2 to go from its up position in FIG. 6 to a down position. Current, therefore, flows to a latch relay 96. Relay 96 closes contacts at 96-2 and 96-3 and opens normally closed contacts at 96-1, 96-4 and 96-5. In spite of the opening of the above described normally closed contacts 96-1, wheel index motor energization continues through LS-2, now in the down position, and contacts 96-2, now closed. Contacts 96-3, also now closed, create a path for current to flow to close spindles" solenoid valve 86 upon the return of limit switch LS-2 to its up position at the end of the indexing movement of wheel 17. Contacts 96-4 are now open in a line to the unlatch mechanism of latch relay 91 and contacts 96-5 are open in the line to open spindles solenoid valve 93.

When the indexing wheel 17 reaches a position in which resistor 11 is adjacent spindles 19, conventional limit switch LS-2 is allowed to spring back to its up position. Wheel index motor 92 is, thus, open circuited, contacts 96-1 now being in open circuit position. Indexing stops, and close spindles solenoid valve 86 is supplied with current to cause pressurized air to actuate the spindles operating assemblies (not shown) to close spindles 19 about leads 12 of resistor 11. Limit switch 13-1 meanwhile opens, since the spindles are no longer in open position, and spindles open relay 94 is dcenergized, causing contacts 94-1 to close and contacts 94-2 to open.

The resistor is now properly held for helixing, while spindles 19 are electrically connected across the resistor. The resistor is also electrically isolated from the cutting mechanlsm.

The closing of the spindles closes a conventional limit switch LS-3 to permit current to flow to a spindles closed relay 84. Relay 84 opens normally closed contacts 84-1, deactivating close spindles solenoid valve 86, and closes contacts 84-2, allowing latching relay 96 to open contacts 96-2 and 96-3 and to return contacts 96-1, 96-4 and 96-5 to their normal closed positions. Since contacts 94-2 are open, wheel index motor 92 continues to be open circuited. The presence of a pair of open contacts 97-1 'keeps the line to open spindles solenoid valve 93 open circuited. Relay 84 may also be used to cause engagement of a spindle clutch and disengagement of a spindle brake (not shown) to permit the rotation of resistor 11.

By this time, cams C-l through C-6 have rotated beyond the zero degree position of FIG. 7. Therefore, testing set testing switch RS-S is closed and current flows to a test set 98. This test, set, of known type, operates to read the resistance of resistor 11 and to close a pair of contacts 99 if and when the resistance measured across resistor 11 is equal to or greater than a control resistance having the desired resistance value. Thus, contacts 99 will be closed if the initial resistance of resistor 11 is greater than the desired resistance value, classifying the resistor as bad. The closing of contacts 99' passes current both to the saw up rotary solenoid 36, which operates the cam 34 to hold saw 22 away from resistor 1'1 in a noncutting position, and to a resistor to value relay 101, which closes a pair of contacts 101-1 to complete a current path between switch RS-5 and a helix length detector switch RS-l. A closed current path through switches RS-S, RS-l and RS-2 and closed contacts at 101-1 and 102-2 will, thus, energize a saw up relay 97. The resultant closing of contacts at 97-5 will keep relay 97 energized until switch RS-2 goes up at degrees. Then switch RS-Z will be in position to continue energization of relay 97 independent of the position of switches RS-l and RS-5. Relay 101 may also be used to cause disengagement of the above-mentioned spindle clutch and engagement of the spindle brake (not shown).

If, on the other hand, the test set 98 does not read an initial resistance for resistor 11 equal to or greater than the desired final resistance value, saw up rotary solenoid 36 will be open circuited, as contacts 99 will remain open. A second pair of contacts 97-2, in a line connected in parallel to the test set contacts '99, is in an open position at this time. Contacts 97-2 can be closed by the actuation of a saw up relay 97. Note that switch RS-l is up and a saw up switch RS-2 is shown by the chart of FIG. 7 to be in the down position on FIG. 7 to be in the down position on FIG. 5 from before the 0 position is reached by the cams to well after 0". Relay 97 is, thus, now open circuited at relay 10*1-1. Since both pairs of contacts 97-2 and 99 are open, saw up rotary solenoid 36 will not be actuated to lift and hold saw 22 away from resistor 11.

Anti-bounce rotary solenoid switch RS-6 is open until associated cam C-6 reaches its 15 position. Rotary solenoid 3 8 is, therefore, open circuited and is not energized to withdraw from the arm 39 on pendulum arm 23 the surface portion of cam 37 which acts as a temporary stop. Thus, saw 22 is suspended close to, but out of contact with the filmed surface of resistor 11.

When the cams attain the 15 position of FIG. 7, switch RS-6 closes. Since normally closed contacts 97-3 remain closed, the saw up relay 97 which causes their closing being open circuited, current fiows to rotary solenoid 38. The stop is retracted from arm 39 and saw 22 moves the small distance to contact the resistance film on resistor '11, from which it will not rebound, and where it is also held at a constant cutting depth, due to the influence of electromagnet 41 on upper end 26 of pendulum arm 23. The electromagnetic flux is controlled by the autotransformer A. Traverse cam 57 is designed to cooperate with cam C-6 for operating switch RS6 so that saw 22 will contact resistor 11 in the proper longitudinal position to start the required helical cut. The continued rotation of traverse cam 57, driven by carriage drive motor 76 for reciprocating the saw carriage, while spindles drive motor 77 rotates spindles 19 and resistor 11 held therein, causes helixing to occur.

Helix length detector switch RS-l is presently in its up position, while switch RS-S is still closed, electrically connecting the resistor to test set 98. When the resistance of resistor 11 reaches the desired value, contacts 99 will close and the saw up rotary solenoid 36 will be energized to remove saw 22 from the surface of the resistor. Resistor to value relay 101, in'parallel with rotary solenoid 36, will simultaneously be actuated to close contacts 101-1. If this point is reached after the 115 down position of helix length detector switch RS-l and prior to the 135 up position of switch RS2, current will flow through normally closed contacts 97-4 to a good resistor relay 102. Cams 57 and C1 are designated to cooperate so that the 115 down position of switch RS-l occurs at a point at which helixing has progressed to 75 percent of the resistor length.

Good resistor relay 102 is actuated if resistor 11 reaches its desired value while cutting within the 75 to 100 percent portion of its length, i.e., while switch RS-l and switch RS2 are both in their down positions between 115 and 135 on the chart of FIG. 7. Relay 102 opens normally closed contacts at 102-1 and 102-2, while closing contacts at 102-3 and 102-4. The opening of contacts 102-1 open circuits the line to rotary solenoid 68, which must be energized to hold segregating gate 66 in the clockwise, bad resistor position of FIG. 2. Thus, gate 66 is caused to attain its good resistor position under the influence of the biasing mechanism (not shown). The open circuit at contacts 102-1 will continue, since contacts 102-3 are now closed. Thus, the closing of segregating gate switch RS-4 at the 90 point on FIG. 7 will keep good resistor relay operative after switch RS-l moves to its down position at 115 and gate 66 will be held in its good resistor position.

In the case of a bad resistor, the resistance will reach value prior to the 115 position on FIG. 7, which corresponds to helixing to 75 percent of the resistor length, or will not reach value prior to the 135 100 percent helixing point. Thus, test set 98 will not signal that the desired resistance value has been reached, causing the closing of contacts 101-1, while switch RS-l is in its down position and switch RS2 is in its down position. Therefore, the good resistor relay 102 will not be energized. Instead, current flow through the contacts of switch RS-4, closed after the 90 point on FIG. 7, and through normally closed closed contacts 102-1 to energize rotary solenoid 68 and maintain the segregating gate in its bad resistor position. The non-energization of good resistor relay 102 is due to the opening of contacts 97-4 by the continued energization of relay 97 if the desired resistance value is reached initially or prior to the 75 percent helixing point, or to the failure of contacts 101-1 to close if the desired resistance value is never reached.

The cutting of a good resistor continues after switch RS-l goes to its down position at the 75 percent point. Since testing continues, switch RS-S remaining closed, saw up rotary solenoid 36 will be energized when test set contacts 99 close upon the resistor reaching its desired resistance value.

At the 135 position on the chart of FIG. 7, switch RS2 goes to its up position. Thus, saw up relay 97 will be energized, independent of its previous condition. Relay 97 closes contacts 97-1 in the line to open spindles solenoid valve 93, while simultaneously closing contacts 97-2 and opening contacts 97-3, both of which tend to remove saw 22 from engagement with the resistors surface if it is still in contact therewith. Solenoid valve 93 will not be actuated, since contacts 91-3 have opened at when switch RS3 went to its up position, causing the unlatching of latch relay 91 to open contacts 91-1, 91-2 and 91-3. The aforementioned normally closed contacts 97-4 are also opened and contacts 974 are closed by relay 97.

At switch RS-l returns to its up position without effect, since switch RS2 is in its up position. Then, at RS3 returns to its down position, causing latch relay 91 to close contacts 91-1, 91-2 and 91-3. The closing of contacts 91-3 energizes solenoid valve 93 to open the spindles 19. The resistor drops out and falls into the selected receptacle 63 or 64, as determined by the attitude of segregating gate 66. Spindles open relay 94 is energized by the closing of LS-l upon the opening of spindles 19. Relay 94 opens normally closed contacts 94-1 to deenergize open spindles solenoid valve 93 and closes contacts 94-2 in the line to wheel index motor 92. The opening of the spindles causes LS-3 to open, open circuiting spindles closed relay 84. Contacts 84-1, thus, close and 84-2 open. An associated spindle clutch (not shown) may be disengaged and an associated spindle brake (not shown) may be engaged by the open circuiting of relay 84.

Saw 22 is now free to be returned by traverse cam 57 toward the initial point of contact with a new resistor. This occurs during the final portion of the cycle of cams C1 through C-6 depicted on FIG. 7, while RS-S, RS-6 and RS2 are successively returned to their initial positions for the start of a new cycle.

So long as power is supplied through main switch 71, cycling will continue until the operation of one of three stops switches 103, 104, or 105, or until a pair of normally closed contacts 89-1 are opened. Contacts 89-1 are opened upon the attainment by the conventional preset counter 89 of a selected number of counts, corresponding to one more than the maximum permissible number of rejections per given time period for continuing operation of the apparatus. Time is measured by conventional generator 88, which is connected to preset counter 89 to periodically reset it to zero, to start counting for another time period. Counter 89 is actuated to add one to the number of counts each time contacts 102-4, in series with counter 89, are closed by energization of bad resistor relay 102.

It is to be understood that the above-described apparatus is simply illustrative of one embodiment of the invention. Alternative electrical circuits may be designed by a person ordinarily skilled in the art to carry out the principles of the invention. The apparatus may easily be adapted to a slabbing operation, cutting a longitudinal, nonhelical groove in the resistance film, by simply not rotating the spindles. Many other modifications may be made without departing from the invention.

What is claimed is:

1. Apparatus for adjusting the resistance of resistor blanks to a desired Valve by cutting a groove having a length greater than a desired minimum length into a resistance film on each resistor blank which comprises:

a support for receiving a succession of said resistor blanks;

a rotary saw mounted adjacent said support for movement into contact with, and along the length of, a resistor blank on said support;

saw driving means for supplying rotary cutting power to said saw;

means operating on said saw for moving the saw from an initial position adjacent said resistor blank into contact with said resistance film on the resistor blank;

traversing means operating on said saw for moving the saw along said resistance film on the resistor blank to cut a groove in the resistance film;

means operating on said saw for removing the saw from the resistor blank and returning it to said initial position when the resistance of the resistor blank reaches said desired value;

a receptacle for finished resistor blanks;

means for delivering said finished resistor blanks to said receptacle; and

means for segregating out from said delivery means resistor blanks having grooves of a length less than said desired minimum length and preventing their delivery to said receptacle.

2. Apparatus for adjusting the resistance of resistor blanks to a desired value as defined in claim 1, which comprises:

means for counting the number of times said segregating means is operated;

a timer, initiated into operation upon the receipt of a first resistor blank in said support, for measuring a predetermined period of time; and

means, rendered effective when said counting means counts a predetermined number of counts before said predetermined period of time is measured by said timer, for shutting down said apparatus.

3. Apparatus for adjusting the resistance of resistor blanks to a desired value as defined in claim 1, wherein said segregating means comprise:

a second receptacle for defective resistor blanks having grooves of a length less than said desired minimum length, said second receptacle mounted adjacent said receptacle for finished resistor blanks;

a gate located adjacent said two receptacles and having two operative positions, said gate blocking finished resistor blanks from entering said second receptacle and permitting the finished resistor blanks to enter said receptacle for finished resistor blanks in a first position, the gate blocking defective resistor blanks from entering said receptacle for finished resistor blanks and permitting the defective resistor blanks to enter said second receptacle in a second position;

means for sensing the presence of defective resistor blanks having grooves of less length than said desired minimum length; and

means responsive to said defective resistor blanks sensing means for maintaining said gate in said second position when a defective resistor blank is sensed and for operating said gate to said first position when a resistor blank is not sensed to be defective.

4. In an apparatus for helixing a path in a carbon film deposited on a ceramic core;

means for gripping and rotating said core;

a rotating saw;

means mounting said saw for movement toward and away from a core in said gripping means and for movement transverse of said core;

an electrical test circuit connected to said gripping means for ascertaining the resistance value of said carbon film;

means actuated by said test circuit ascertaining that said resistance film is below a predetermined value for operating said mounting means to move said saw into engagement with said core;

means rendered efiective upon movement of said saw for moving said saw transverse of said rotating core to cut a helical path in said carbon film;

a receptacle for helixed cores;

means for delivering said helixed cores to said receptacle;

means for removing cores having resistance films of a resistance greater than said predetermined value from said gripping and rotating means and segregating said removed cores from said receptacle;

means for counting the number of times said removing and segregating means is operated;

a timer, initiated upon first ascertaining the initial resistance value of said carbon film by said electrical test circuit, for measuring a predetermined period of time; and

means, rendered etfective when said counting means counts a predetermined number of counts before Cir said predetermined period of time is measured by said timer, for shutting down said apparatus.

5. In an apparatus for helixing a path in a carbon film deposited on a ceramic core as set forth in claim 4;

a second receptacle for defective cores having carbon films of a resistance greater than said predetermined value, said second receptacle mounted adjacent said receptacle for helixed cores;

a gate, forming a part of said removing and segregating means, located adjacent said two receptacles and having two operative positions, said gate blocking helixed cores from entering said second receptacle and permitting the helixed cores to enter said receptacle for helixed cores in a first position, the gate blocking defective cores having film resistances above said predetermined value from entering said receptacle for helixed cores and permitting said defective cores to enter said second receptacle in a second position;

means biasing said gate toward said second position;

a rotary solenoid, normally energized to counteract the efiect of said biasing means and to normally maintain said gate in said first position; and

means actuated by said test circuit ascertaining that the resistance of the film on the core is above said predetermined value for reenergizing said rotary solenoid to cause said biasing means to operate said gate to said second position.

6. In an apparatus for helixing a path in a carbon film deposited on a ceramic core as set forth in claim 5:

means, rendered effective upon said test circuit determining prior to helixing of said core over a minimum length that said predetermined resistance value has been reached, for deenergizing said rotary solenoid to cause said biasing means to operate said gate to said second position and for registering a count on said counting means.

7. In an apparatus for helixing deposited carbon resistors to value and for sorting said helixed resistors in accordance with initial and final parameters:

means for releasably holding and rotating a deposited carbon resistor;

means for removing carbon from said resistor;

means for advancing said removing means toward said resistor to remove said carbon;

means for traversing said advancing means longitudinally of said rotating resistor to remove a helix of carbon;

a movable gate located to receive a resistor dropped from said holding means and selectively positionable between a first position indicative of a resistor having acceptable initial and final parameters and a second position indicative of a resistor having unacceptable parameters;

means for measuring said initial and final parameters;

means responsive to initial and final parameters measured for moving said gate selectively between said first and second positions and means responsive to the completion of the traverse of said carbon removing means for releasing said holding and rotating means to drop the resistor onto said selectively positioned gate.

8. An apparatus for helixing deposited carbon resistors to value and for sorting said helixed resistors in accordance with initial and final parameters, as defined in claim 7, wherein said parameter measuring and gate moving means comprise:

means for measuring the resistance value of the resistor;

means, responsive to an initial resistance measured by said resistance measuring means at above a predetermined value, for precluding the advance of said removing means toward said resistor and for moving said gate from said first position to said second position;

sistive film on a blank, comprising:

means for supporting a "blank,

means for removing the resistive film from said blank to form a resistor,

means for imparting relative movement between said film removing means and said support means to remove a portion of said film,

means for measuring the resistance value of the film while said film is being removed,

means responsive to said measuring means ascertaining a predetermined resistance value for interrupting said relative movement of said removing means and said support means to terminate the removal of film,

means actuated after operation of said interrupting means for releasing said resistor from said support means,

means for receiving a released resistor as a finished,

acceptable article,

means selectively operated for guiding a released resistor to or away from said receiving means, and

means actuated after the passage of a predetermined period of time from the start of removal of said film and the failure of said measuring means to measure said predetermined resistance value for selectively operating said guiding means in a condition to guide a released resistor away from said receiving means and operating said interrupting means to terminate the removal of film.

10. Apparatus for adjusting film resistance values, as

set forth in claim 9, further comprising:

means for counting the number of times that said releasing means is operated with said guiding means in said condition to guide a released resistor away from said receiving means, and

means responsive to a predetermined number of counts within a predetermined time period for shutting down the apparatus.

11. In an apparatus for increasing the effective resistance value of material formed on an elongated article:

means for removing material from the article;

means for imparting longitudinal relative movement between said elongated article and said material removing means to remove a portion of the material from the article and increase the effective resistance of the remaining material;

means responsive to the removal of a suflicient amount of material to increase the effective resistance value of the remaining material to a predetermined value for interrupting operation of said material removing means; and

means actuated upon said predetermined value being reached and said interrupting means operating after the impartation of a predetermined relative movement between said article and said material removing means for generating a signal indicative of said predetermined value being reached after completion of said predetermined relative movement.

References Cited UNITED STATES PATENTS 2,773,332 12/1956 Buchman et al. 51-319 X 2,884,746 5/1959 Rus et a1 51-165 X 2,992,730 7/1961 Rayburn et a1 209-81 3,082,871 3/ 1963 Duncan 209-81 3,105,288 10/1963 Johnson et a1 51-105 X 3,138,065 6/1964 Owens et a1 51-50 X 3,357,139 12/ 1967 Ianuzzi et a1 51-50 ANDREW R. JUHASZ, Primary Examiner.

G. WEIDENFELD, Assistarz't Examiner.

US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,444 782 May 20 1969 Nicholas J. Mandonas et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 65, "section" should read sectional Column 4 line 14 "member" should read members Column 6 line 21, after "test" cancel the comma; line 52, cancel "to be in the down position on FIG. 7". Column 7 line 51 after "current" insert will Column 8 line 38 after "conventional" insert pulse Column 10, line 26, "reenergizing" should read deenergizing line 54, after table" insert initial and final lines 56-58 element not indicated as a separate element line 58 after "position" insert a semi-colon. Column 12 line 23 after "resistance" insert value Signed and sealed this 24th day of March 1970.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

